MundoKit

SLA uptime & downtime calculator

Enter an availability target to see how much downtime it allows per day, week, month, quarter and year. Add components in series to see how dependencies stack up.

Inputs
%
For example 99.9 for “three nines”.
How many services must all be up at once, each with this availability and failing independently. Use 1 for a single service.

Results

Allowed downtime per month
43m 48s
Allowed downtime per year
8h 45m 36s
Effective availability
99.9%
Downtime budget at 99.9% availability
PeriodAllowed downtimeMinutes
Per day1m 26s1.44 min
Per week10m 5s10.08 min
Per month (1/12 year)43m 48s43.8 min
Per quarter2h 11m 24s131.4 min
Per year (365 days)8h 45m 36s525.6 min

Results update as you type. The share link stores your inputs after the # in the address, which is not sent to our server, but anyone you send it to can read them.

How it works

Downtime allowed by a target is the unavailable fraction multiplied by the length of the period:

downtime = (1 − availability ÷ 100) × period

We use a 365-day year, a month of one twelfth of a year (365 ÷ 12 = 30.4167 days) and a quarter of one quarter of a year. Providers sometimes measure per calendar month instead, so a 31-day month allows slightly more downtime than shown.

When several services must all be up at the same time (in series) and fail independently, their availabilities multiply: two services at 99.9% give 0.999 × 0.999 = 99.8001%. If they share infrastructure and fail together, the combined figure is closer to the single-service value, so treat the product as the worst case for independent failures.

Rounding: durations are rounded to the nearest second; a positive budget under one second is shown in milliseconds so it never appears as zero. Minutes are shown to four decimals.

Worked examples

99.9% (“three nines”) for one service

(1 − 0.999) × (365 ÷ 12) days × 86,400 s = 2,628 s, which is 43m 48s per month and 8h 45m 36s per year.

Three independent dependencies at 99.95% each

0.9995³ = 0.998501, so the combined service is up 99.8501% of the time and may be down about 1h 5m 40s per month.

Frequently asked questions

How much downtime is 99.99% uptime?
About 52m 34s per year, 4m 23s per month and 8.6 seconds per day.
What is an error budget?
An error budget is the downtime (or failed requests) your target still allows. If the SLO is 99.9% per month, the budget is about 43 minutes; teams use it to decide how much risk a release can take.
Why does my provider’s number differ slightly?
Providers define the month differently (calendar month, 30 days or 730 hours) and may exclude scheduled maintenance. Check the definition in their SLA.

Sources

Last reviewed 2026-11-14. The method is written out above so you can check our math.